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Chromatin Structure Overview to Histone Deacetylation6Topics
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Nucleoside and Nucleotide Basics to Base Pairing and DNA Stability5Topics
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Introduction to Nucleotide Synthesis Inhibition to Broad-Spectrum Inhibitors and CPS Enzymes5Topics
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Purine Metabolism and Salvage Pathways to Genetic Code: Commaless and Universal6Topics
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DNA Replication Basics to Detailed Lagging Strand Synthesis7Topics
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DNA Repair: Nonhomologous End Joining to DNA Repair: Mismatch Repair5Topics
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Introns vs Exons: Basic Definitions to Visualizing Alternative Splicing and Protein Diversity4Topics
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tRNA Structure Overview to mRNA Stop Codons6Topics
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Introduction to DNA Mutations to Lac Operon Gene Expression States8Topics
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Cilia Structure: Motile Cilia and Basal Body to K+ Pump Inhibition6Topics
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Page 1 — Eukaryotic Gene Overview to Page 1 — RNA Processing: Splicing & Fate8Topics
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Osteogenesis Imperfecta: Genetic Basis to Menkes Disease6Topics
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Eukaryotic RNA Polymerases: Types to Splicing Diagram: Lariat & Mature mRNA7Topics
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Flow Cytometry: Basics and Applications to ELISA: Principle and Uses4Topics
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Protein Synthesis: Initiation Phase to Posttranslational Modifications: Chaperone Proteins6Topics
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Karyotyping: Principles and Applications to Molecular Cloning: Process and Applications4Topics
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Cell Cycle Phases and Regulation to p53 and Apoptosis Induction7Topics
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Introduction to Imprinting Disorders to Visualizing Normal vs. Mutated Chromosomes6Topics
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Rough Endoplasmic Reticulum Functions to Specific Vesicular Trafficking Proteins7Topics
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Autosomal Dominant Inheritance to Pedigree Chart Symbols6Topics
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Peroxisome Functions to Drugs Affecting Microtubules5Topics
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Polyunsaturated Essential Fatty Acids to Water-Soluble Vitamins: Deficiencies and Coenzyme Functions5Topics
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Collagen Introduction and Type I to Collagen Synthesis: Maturation and Fibril Formation6Topics
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Vitamin B7 (Biotin): Function and Deficiency to Vitamin B9 (Folate): Deficiency, Causes, and Prevention3Topics
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Elastin: Structure and Composition to PCR Cycle: Elongation and Repetition8Topics
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Ethanol Metabolism Overview to Pharmacological Interventions in Alcohol Metabolism5Topics
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CRISPR to Interpreting Southern Blot Results5Topics
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Key Metabolic Locations to Glucose Breakdown and NADPH Production4Topics
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Transgenic Strategies in Mice to Epistasis and Aneuploidy7Topics
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Pyruvate Dehydrogenase Deficiency to The TCA Cycle (Krebs Cycle)3Topics
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Genetic Terms: Dominant Negative & Linkage Disequilibrium to Conditions for Hardy-Weinberg Equilibrium7Topics
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ETC Overview to Fatty Acids in Gluconeogenesis9Topics
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Autosomal Dominant Disorders to CFTR Channel Function Diagram11Topics
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Phenylketonuria: Basic Defect and BH4 Deficiency to Alkaptonuria7Topics
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X-linked Recessive Diseases Introduction to Myotonic Dystrophy6Topics
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Fatty Acid Synthesis Overview to Medium-Chain Acyl-CoA Dehydrogenase Deficiency4Topics
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Mitochondrial Diseases: MELAS & MERRF to Trinucleotide Repeat Diseases: Fragile X & Friedreich Ataxia8Topics
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Hepatic Ketone Body Synthesis to Adipocyte Metabolism: Fed State4Topics
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Autosomal Trisomies & Down Syndrome Overview to Second Trimester Screening & NIPT8Topics
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Metabolic Fuel Use: Initial Exercise to Starvation After Day 3 and Stored Energy Depletion7Topics
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Genetic Disorders: Chromosomes 3-7 to Williams Syndrome6Topics
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Dietary Lipid Absorption and Chylomicron Entry to IDL, LDL Formation, and Uptake4Topics
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Vitamin A: Functions and Forms to Vitamin B1: Beriberi Forms7Topics
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Vitamin B2: Function and Deficiency to Vitamin B6 Deficiency Symptoms7Topics
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Vitamin B12: Name, Function, and Sources to Vitamin C: Excess and Toxicity7Topics
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Vitamin D Introduction and Function to Vitamin E Deficiency and Excess Effects6Topics
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Vitamin K Function to Marasmus: Characteristics and Visuals7Topics
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Enzyme Terminology: Kinase & Phosphorylase to Rate-Determining Enzymes: Lipid Metabolism7Topics
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ATP Production Pathways to Hexokinase vs Glucokinase: Kinetics & Regulation5Topics
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Glycolysis Net Reaction to PDC: α-Ketoglutarate & Arsenic7Topics
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Introduction to Pentose Phosphate Pathway to G6PD Deficiency: Biochemical Mechanism of Oxidative Stress7Topics
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Essential Fructosuria to Galactose Metabolism Pathway & Summary6Topics
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Sorbitol Pathway and Diabetic Complications to Acidic and Basic Amino Acids6Topics
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Urea Cycle Introduction to Hyperammonemia Treatment5Topics
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Ornithine Transcarbamylase Deficiency to Catecholamine Synthesis and Degradation5Topics
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Homocystinuria: Genetic Causes to Methylmalonic Acidemia: Deficiency & Metabolism6Topics
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Glucagon to Glycogen Disorders and Enzymes6Topics
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Introduction to Glycogen Storage Diseases to McArdle Disease (Type V)6Topics
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Lysosomal Storage Diseases Intro & Tay-Sachs to Lysosomal Storage Disease Pathway6Topics
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Key Enzymes in Lipid Transport - Part 1 to Major Apolipoproteins - Part 25Topics
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Lipoprotein Functions: Chylomicron & VLDL to Familial Dyslipidemias: Dysbetalipoproteinemia & Hypertriglyceridemia5Topics
Chromatin Structure Overview to Histone Deacetylation
Content August 26, 2025
Chromatin structure
DNA exists in the condensed, chromatin form to fit into the nucleus. DNA loops twice around a histone octamer to form a nucleosome (“beads on a string”). H1 binds to the nucleosome and to “linker DNA,” thereby stabilizing the chromatin fiber.
DNA has ⊖ charge from phosphate groups. Histones are large and have ⊕ charge from lysine and arginine.
In mitosis, DNA condenses to form chromosomes. DNA and histone synthesis occurs during S phase.
Mitochondria have their own DNA, which is circular and does not utilize histones.
Heterochromatin
Condensed, appears darker on EM (labeled H in A, nucleolus). Sterically inaccessible, thus transcriptionally inactive. ↑ methylation, ↓ acetylation.
Heterochromatin = highly condensed. Barr bodies (inactive X chromosomes) may be visible on the periphery of nucleus.
Euchromatin
Less condensed, appears lighter on EM (labeled E in A). Transcriptionally active, sterically accessible.
Eu = true, “truly transcribed.” Euchromatin is expressed.
DNA methylation
Changes the expression of a DNA segment without changing the sequence. Involved with aging, carcinogenesis, genomic imprinting, transposable element repression, and X chromosome inactivation (lyonization).
DNA is methylated in imprinting. Methylation within gene promoter (CpG islands) typically represses (silences) gene transcription. CpG methylation makes DNA mute. Dysregulated DNA methylation is implicated in Fragile X syndrome.
Histone methylation
Usually causes reversible transcriptional suppression, but can also cause activation depending on location of methyl groups.
Histone methylation mostly makes DNA mute. Lysine and arginine residues of histones can be methylated.
Histone acetylation
Removal of histone’s ⊕ charge → relaxed DNA coiling → ↑ transcription.
Thyroid hormone receptors alter thyroid hormone synthesis by acetylation. Histone acetylation makes DNA active.
Histone deacetylation
Removal of acetyl groups → tightened DNA coiling → ↓ transcription.
Histone deacetylation may be responsible for the altered gene expression in Huntington disease.
Topics Covered:
- Chromatin Structure Overview
- Heterochromatin vs. Euchromatin
- DNA Methylation
- Histone Methylation
- Histone Acetylation
- Histone Deacetylation